Galera Cluster InstallationAnd Quick Start

Philip StoevCodership Oy

2

CodershipEstablished 2007 (Galera development started)

3 co-founder engineers:Seppo Jaakola, CEO, Teemu Ollakka, CTO, Alex Yurchenko, architectTeam have developed three MySQL cluster software earlier.

Based on: http://www.dsn.jhu.edu/~yairamir/Yair_phd.pdfhttp://www.inf.usi.ch/faculty/pedone/Paper/199x/These-2090-Pedone.pdf

Product: Galera Cluster for MySQL, open source

Thousands of users in e-commerce, telecom, gaming, insurance, betting healthcare, media, marketing, advertising, travel, universities, software-as-service, Paas, Iaas, etc

Galera Cluster is included and will be included in Linux and OpenStack distros

3

Galera Cluster variants

API

MySQL

Coderhips’s Galera Replication plugin

API

PerconaServer

API

MariaDB

mergemerge

Percona calls Galera Percona XtraDB Cluster

Galera Cluster for MySQL by CodershipMariaDB calls Galera MariaDB Galera Cluster or MariaDB Enterprise Cluster

Agenda• A very quick overview of Galera Cluster• Adding the Galera package repository• Installing packages• Creating a configuration file• Bootstrapping a 3-node cluster• Monitoring

Galera Cluster OverviewSynchronous

– each transaction is immediately replicated on all nodes at commit– no stale slaves

Multi-Master– read from and write to any node– automatic transaction conflict detection

Replication– a copy of the entire dataset is available on all nodes– new nodes can join automatically

For MySQL– based on a modified version of MySQL (5.5, 5.6 with 5.7 coming up)– InnoDB storage engine

And more …• Recovers from node failures within seconds• Data consistency protections

– avoids reading stale data– prevents unsafe data modifications

• WAN support– nodes can be on different continents– end-to-end encryption– optimized communication with least latency

Package Installation (CentOS, RHEL)1. Remove existing MySQL server packages 2. Configure the Galera Cluster repository

Add a .repo file in /etc/yum.repos.d/:[galera]name = Galerabaseurl = http://releases.galeracluster.com/centos/7/x86_64 gpgkey = http://releases.galeracluster.com/GPG-KEY-galeracluster.comgpgcheck = 1

(note distribution name and release number are specified)

3. Install Galera Cluster Packagesyum –y upgrade mysql-wsrep-shared-5.6

yum –y install galera-3 mysql-wsrep-5.6

Preparing the System• Nodes should have identical hardware• Firewall ports to open:

3306, 4567, 4568, 4444• Disable SELinux

– a policy can be created and enabled later

The my.cnf Configuration File• All Galera configuration is in my.cnf• Keep the my.cnf files on all nodes identical• InnoDB settings are important

optimize individual nodes as you normally would:– InnoDB buffer size– InnoDB log file size

• Galera-specific settings:default_storage_engine=InnoDBbinlog_format=ROWinnodb_autoinc_lock_mode=2wsrep_provider=/usr/lib64/galera-3/libgalera_smm.so wsrep_cluster_address="gcomm://node1,node2,node3... "

Bootstrap1. Start first node with –wsrep-new-cluster:

sudo service mysql start --wsrep-new-cluster

2. Confirm a single-node cluster:SHOW STATUS LIKE 'wsrep_%'| wsrep_cluster_status | Primary || wsrep_cluster_size | 1 |

3. Start all other nodes normallysudo service mysql start

4. Confirm nodes have joined:SHOW STATUS LIKE 'wsrep_%'| wsrep_cluster_size | 3 |

Monitoring

Traditional MySQL monitoring methods are used:• SHOW STATUS• SHOW PROCESSLIST• The MySQL error log

– all Galera messages go there• Queries against INFORMATION_SCHEMA

SHOW STATUS• Node health variables:

– wsrep_ready = ON– wsrep_cluster_size– wsrep_cluster_status = Primary– wsrep_local_status = Synced

• Replication health variables:– wsrep_flow_control_paused < 0.05– wsrep_local_bf_aborts + wsrep_local_cert_failures

(do not forget periodic FLUSH STATUS)

SHOW PROCESSLIST• Queries to watch out for:

– long “Query end” phase• replication takes place during that phase

– long-running DDL• under default settings may block cluster

INFORMATION_SCHEMA• Avoid non-InnoDB tables:

SELECT TABLE_SCHEMA, TABLE_NAME FROM INFORMATION_SCHEMA.TABLES WHERE ENGINE != 'InnoDB'AND TABLE_SCHEMA NOT IN ('mysql','performance_schema', 'information_schema');

• Avoid tables with no primary key:

SELECT T.TABLE_SCHEMA, T.TABLE_NAME FROM information_schema.tables AS T WHERE (table_schema, table_name)NOT IN (SELECT table_schema, table_name FROM information_schema.table_constraints AS C WHERE T.table_name = C.table_name AND T.table_schema = C.table_schema )AND table_schema NOT IN ('mysql','information_schema','performance_schema');

Thank You

Downloads, documentation:

http://www.galeracluster.com

Discussion group:

codership-team@googlegroups.com